The present invention relates to a chair seat tilting mechanism.
Various types of office chairs are known that have a tiltable chair back and a chair seat tiltably mounted to a spindle. In one arrangement, when an occupant leans back in the chair, both the chair back and the chair seat tilt backwardly. This arrangement is disadvantageous in that the backward tilt of the chair seat may reduce blood circulation to the legs and prevent the occupant from assuming a completely comfortable position. An alternative arrangement alleviating these problems has been developed wherein the chair seat tilts forwardly when an occupant leans back in the chair. A mechanism consistent with this arrangement, described in U.S. Pat. No. 5,573,303 (the disclosure of which is hereby incorporated herein by reference), employs a link arm with a cam, a lever arm and a support that are mounted and arranged such that the desired forward tilting of the chair seat occurs when an occupant reclines the chair back.
A shortcoming of known chair seat tilting mechanisms is their inability to permit the front of the chair seat to tilt downwardly without the chair back tilting backwardly. A chair occupant may assume various positions, by extending one""s legs forward with knees locked for example, in which increased downward pressure is applied to the front of the chair seat. This increased pressure may reduce circulation to the occupant""s legs or otherwise result in discomfort on the part of the occupant. In such situations it would be desirable to have a mechanism in which the front of the chair seat tilts downwardly to relieve pressure on the occupant""s legs even when the chair back is not tilted backwardly.
This invention seeks to provide an alternative to the forwardly tilting chair seat mechanism disclosed in U.S. Pat. No. 5,573,303 and which overcomes the drawback of known mechanisms.
It is an object of the present invention to provide a chair seat tilting mechanism wherein the chair seat tilts forwardly when an occupant leans back in the chair.
Advantageously, the mechanism may further allow the chair seat to tilt forwardly, without backwardly tilting the chair back, upon the application of an overriding downward force onto the front of the seat.
In accordance with an aspect of the present invention there is provided a chair seat tilting mechanism, comprising: a main frame for mounting to a seat spindle; a seat plate pivotable with respect to said main frame about a rearward pivot, said rearward pivot having limited lateral translational freedom with respect to said main frame; a back bracket pivotable with respect to said main frame about a forward pivot; and a medial pivot pivotably connecting said seat plate to said back bracket, said medial pivot medially positioned between said rearward pivot and said forward pivot such that pivoting said back bracket about said forward pivot in one direction draws said medial pivot downwardly so as to tilt said seat plate forwardly.
In accordance with another aspect of the present invention there is provided a chair seat tilting mechanism, comprising: a main frame for mounting to a seat spindle; a seat plate for mounting to a seat; a back bracket for mounting to a chair back; a rearward pivot pivotably connecting said seat plate to said main frame; means for permitting limited lateral translational freedom of said rearward pivot with respect to said main frame; a forward pivot pivotably connecting said back bracket to said main frame; and a medial pivot pivotably connecting said seat plate to said back bracket, said medial pivot medially positioned between said rearward pivot and said forward pivot such that pivoting said back bracket about said forward pivot in one direction draws said medial pivot downwardly so as to tilt said seat plate forwardly.
In accordance with still another aspect of the present invention there is provided a chair having a seat tilting mechanism, comprising: a chair spindle; a main frame mounted to said spindle; a seat plate pivotable with respect to said main frame about a rearward pivot, said rearward pivot having limited lateral translational freedom with respect to said main frame; a seat mounted to said seat plate; a back bracket pivotable with respect to said main frame about a forward pivot; a medial pivot pivotably connecting said seat plate to said back bracket, said medial pivot medially positioned between said rearward pivot and said forward pivot such that pivoting said back bracket about said forward pivot in one direction draws said medial pivot downwardly so as to tilt said seat plate forwardly; and a chair back mounted to said back bracket.